Traditional center pivot steered construction machines, especially wheel loaders, rocker dump trucks, or wheel-linked farm tractors, construction or special machines, are equipped with load-changeable transmission mechanisms, comprising torque converters or fluid couplings or hydrostatic drives. In most such service and working vehicles, such as the wheel loaders, a permanent four-wheel drive is provided, being realized on the power take-off from the gearbox with a fixed torque distribution between front and rear axle.
The permanent four-wheel drive can have negative effects in some operating conditions. For example, the permanent four-wheel drive can result in an increased fuel consumption, as well as decreased driving features and driving performance. Furthermore, the permanent four-wheel drive can result in a needlessly large mechanical load on the drive components and increased tire wear.